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tint/uniformity: Fix handling of continuing block 

Variables declared inside a loop block were not visible to the
continuing block. Special-case the continuing block by processing it
inside the loop-body block statement, instead of afterwards.

Change-Id: I05bc906bd98b24295dc91116b9ef8d8ef02c3af3
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/114860
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: James Price <jrprice@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>
This commit is contained in:
James Price 2022-12-20 20:12:51 +00:00 committed by Dawn LUCI CQ
parent efc9df4695
commit eb34a764a8
2 changed files with 85 additions and 6 deletions
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24
src/tint/resolver/uniformity.cc
View File

@ -462,6 +462,22 @@ class UniformityGraph {
}
}
auto* parent = sem_.Get(b)->Parent();
auto* loop = parent ? parent->As<sem::LoopStatement>() : nullptr;
if (loop) {
// We've reached the end of a loop body. If there is a continuing block,
// process it before ending the block so that any variables declared in the
// loop body are visible to the continuing block.
if (auto* continuing =
loop->Declaration()->As<ast::LoopStatement>()->continuing) {
auto& loop_body_behavior = sem_.Get(b)->Behaviors();
if (loop_body_behavior.Contains(sem::Behavior::kNext) ||
loop_body_behavior.Contains(sem::Behavior::kContinue)) {
cf = ProcessStatement(cf, continuing);
}
}
}
if (sem_.Get<sem::FunctionBlockStatement>(b)) {
// We've reached the end of the function body.
// Add edges from pointer parameter outputs to their current value.
@ -860,13 +876,11 @@ class UniformityGraph {
current_function_->variables.Set(v, in_node);
}
// Note: The continuing block is processed as a special case at the end of
// processing the loop body BlockStatement. This is so that variable declarations
// inside the loop body are visible to the continuing statement.
auto* cf1 = ProcessStatement(cfx, l->body);
if (l->continuing) {
auto* cf2 = ProcessStatement(cf1, l->continuing);
cfx->AddEdge(cf2);
} else {
cfx->AddEdge(cf1);
}
cfx->AddEdge(cf);
// Add edges from variable loop input nodes to their values at the end of the loop.

65
src/tint/resolver/uniformity_test.cc
View File

@ -1545,6 +1545,71 @@ fn foo() {
RunTest(src, true);
}
TEST_F(UniformityAnalysisTest, Loop_NonUniformValueDeclaredInBody_UnreachableContinuing) {
std::string src = R"(
@group(0) @binding(0) var<storage, read_write> non_uniform : i32;
fn foo() {
var condition = true;
loop {
var v = non_uniform;
if (condition) {
break;
} else {
break;
}
continuing {
if (v == 0) {
workgroupBarrier();
}
}
}
}
)";
RunTest(src, true);
}
TEST_F(UniformityAnalysisTest, Loop_NonUniformValueDeclaredInBody_MaybeReachesContinuing) {
std::string src = R"(
@group(0) @binding(0) var<storage, read_write> non_uniform : i32;
fn foo() {
var condition = true;
loop {
var v = non_uniform;
if (condition) {
continue;
} else {
break;
}
continuing {
if (v == 0) {
workgroupBarrier();
}
}
}
}
)";
RunTest(src, false);
EXPECT_EQ(error_,
R"(test:16:9 warning: 'workgroupBarrier' must only be called from uniform control flow
workgroupBarrier();
^^^^^^^^^^^^^^^^
test:15:7 note: control flow depends on non-uniform value
if (v == 0) {
^^
test:7:13 note: reading from read_write storage buffer 'non_uniform' may result in a non-uniform value
var v = non_uniform;
^^^^^^^^^^^
)");
}
TEST_F(UniformityAnalysisTest, Loop_NonUniformBreakInBody_Reconverge) {
// Loops reconverge at exit, so test that we can call workgroupBarrier() after a loop that
// contains a non-uniform conditional break.